For decades dental professionals have been taught a denture tooth selection procedure that is primarily based on the theory that the shape of a person's head or arch form corresponds to the shape of their teeth. Thus, shortly before World War I, J. Leon Williams presented a correlation between tooth form and the shape of a person's head. Thus the square, tapering, ovoid “William's Classification” was born. According to this theory, an inverted maxillary incisor tooth has roughly the same shape as the person's face, both in the profile and the frontal view. Although the validity of this theory has since been questioned by numerous authors, it remains today as the predominant feature of current mold guides due primarily to the stagnation of innovation in the field of removable prosthodotnics. Basic tooth forms have been established based on this concept, namely square, tapering, and ovoid.
It has proved to be an inexact, subjective analysis that is unpredictable and rarely repeatable. Unfortunately denture tooth mold guides have followed this same theory and continue to be organized according to square, tapering, and ovoid tooth forms. This classification has been handed down throughout the ages with minimal scientific merit or practical application and is not considered to be a significant tool for anterior tooth selection. The result of this ineffective denture tooth selection process is that dentists have withdrawn from the process of selecting denture teeth. This critical decision has been relegated to the technicians, who have grown comfortable with their favorite brands and molds of teeth and tend to select only from a limited number of molds. The technician unfortunately does not have the opportunity to view the patient and therefore make an informed decision based on the patient's many characteristics (sex, personality, age, neuromuscular status, denture history, etc).
Numerous investigators have suggested a correlation between the intercanine distance and the interalar width of the nose. The Swissedent investigators recorded the interalar width of the nose with an instrument, and then placed the pointers of the instrument against the natural maxillary canines. They found that, in 75% of their subjects, the pointers indicated approximately the center areas of the canines. This investigation resulted in the development of the Swissedent® Alameter. Boucher suggested projecting perpendicular lines downward from the alae of the nose to the buccal surface of a maxillary occlusion rim in the mouth. Marks are made on the occlusion rim which are used to position the tips or distal edges of the artificial canines. To select the correct size of an artificial tooth, the distance between the canine marks is measured around the curve of the occlusion rim with a flexible rule. Six maxillary anterior teeth are chosen with an over-all width equal to this measurement. Further investigation of this relationship was mathematically analyzed to more accurately determine maxillary anterior mold selection. Drs. Fisher and Frush introduced the concept of Dentogenics to the profession. Dentogenics is a concept that suggests various alterations of tooth morphology and position of teeth that follows individual patient characteristics (sex, personality, age). Tooth molds with feminine attributes were typified by gentle, rounded features, which suggest softness and smoothness. Conversely masculine tendencies were characterized in dentogenics by robust, cuboidal forms that expressed strength, vigor, and boldness. The organization of anterior mold morphology according to “softness” and “boldness” is a generally accepted classification of anterior tooth morphology and is commonly used in the tooth selection process.